Funding for this research was provided by:
National Natural Science Foundation of China (31472054)
The National Research Foundation for the Doctor Program of Higher Education of China (20120162110058)
Text and Data Mining valid from 2018-08-24
Received: 23 March 2018
Accepted: 13 August 2018
First Online: 24 August 2018
Ethics approval and consent to participate
: The study was sanctioned by the ethics committee of the Reproductive and Genetic Hospital of CITIC-Xiangya. Due to the retrospective nature of the study, informed consent was waived.
: Not applicable.
: The authors declare that they have no competing interests.
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